Two information services found in households and businesses today include television, or video, services and telephone services. Another information service involves digital data transfer which is most frequently accomplished using a modem connected to a telephone service. All further references to telephony herein shall include both telephone services and digital data transfer services.
Characteristics of telephony and video signals are different and therefore telephony and video networks are designed differently as well. For example, telephony information occupies a relatively narrow band when compared to the bandwidth for video signals. In addition, telephony signals are low frequency whereas NTSC standard video signals are transmitted at carrier frequencies greater than 50 MHz. Accordingly, telephone transmission networks are relatively narrow band systems which operate at audio frequencies and which typically serve the customer by twisted wire drops from a curb-side junction box. On the other hand, cable television services are broad band and incorporate various frequency carrier mixing methods to achieve signals compatible with conventional very high frequency television receivers. Cable television systems or video services are typically provided by cable television companies through a shielded cable service connection to each individual home or business.
An improved communication system utilizing both a fiber optic network and a co-axial cable transmission and distribution network has been developed. The system generally provides both telephony service and video service through the same medium to homes and businesses. The system replaces the prior separate transmission media commonly used today. Such a system is disclosed in co-pending U.S. patent application Ser. No. 08/384,659 filed on Feb. 6, 1995 and assigned to the assignee of the present invention.
The traditional telephony system utilizes a network interface device (NID) usually attached to an exterior wall of a home. The ND receives and transmits telephony signals from and to the junction box and receives and selectively distributes signals from and to the various electronics devices in a home or business such as telephones and computers. A separate video signal is transmitted over a coaxial cable network by the service provider and selectively distributed via shielded co-axial cables routed to subscribing homes and business.
The new system requires a new interface device for housing a modulator-demodulator (modem) which receives and separates the various telephony and video signals and distributes the various signals to the appropriate locations or devices. The modem and other electronics necessary for receiving and transmitting incoming signals must be securely protected from exposure to weather conditions. The electronics of the modem also generate a large amount of waste heat that, if not properly dissipated, causes damage and life reduction or failure of the electronic components of the electronics of the units.
These problems and others, as will become apparent from the description herein, present a need for an improved home integrated service unit for an enhanced communication system.